Oven



Dec. 23, 1941. A. H. cHENowETH 2,266,957

OVEN

Filed March 29, 1940 2 sheets-sheet 1 Il l CQ l 114 v 7a 1M 5 W k 76; kw fa R 154 1j 1108 42% @4 94 7580 so NVENTOR WITNESS ATTORNEYS Dec. 23, 1941. A. H. cHENowETH OVEN Filed March 29, 1940 2 Sheets-Sheet 2 WITNESS Patented Dec. 23, 1941 UNITED STATES PATENT OFFICE OVEN Avery H. Chenoweth, Mason City, Ill. Application March 29, 1940, Serial No. 326,808

14 Claims.

My invention relates to artificial dentures, and has among its objects and advantages the provision of an improved dry heat method of and oven for curing such dentures.

At the present time, many recently developed types of synthetic resinous materials are being used in the making of dentures, such as, acrylic (sold under the trade name Crystolex) and phenol formaldehyde resin (sold under the trade name Luxene 37). Such denture materials are extremely light in weight, durable, and dense so as to be characterized by relatively low moisture absorption properties. Dentures formed of such materials are exceptionally attractive in color and texture, with the color simulating natural oral tissue. While the properties of such denture materials are entirely satisfactory so far as strength, color, density and lightness in Weight are concerned, considerable diiliculty has been experienced in the matter made therefrom.

Many systems have been devised for the curing of artiilcial dentures, particularly with respect to heat application. Steam has been employed quite generally, while dry heat methods have been attempted with little success. Because of the peculiar properties of denture materials of the above mentioned type, dry heat curing has many advantages over the steam methods. In curing dentures, the temperature must be accurately controlled, but the problem of moisture elimination, so far as direct contact between the moisture and the denture is concerned, is equally important.

It is common practice to employ tin foil for the purpose of shielding the denture from contact with moisture during the curing process. Any break in the tin foil which permits moisture contact results in discoloration of the denture, such as the formation of white spots, and a good bond between the teeth and the plate can be had only through proper elimination of moisture. Tin foiling is a tedious and time consuming job, and it frequently happens that the tin foil assumes a wrinkled condition which leaves grooves and surface irregularities in the denture. Then, too, the tin foil covering prevents the plate structure from conforming in size and shape eX- actly to the mold.

Accordingly, an object of my invention is to provide novel means for dry heat curing of dentures without the use of tin foil, in which the dentures may be accurately formed to size and shape, and in which a perfect bond may be secured between the teeth and the plate, as well as uniform coloration.

of curing dentures More speciilcally, I provide a curing oven having a relatively thick metal plate which supports the ilask, with the plate located above a heating element inside the oven. A relatively thick metal plate is positioned on the top of the ilask and is located underneath a second heating element inside the oven. The flask bottom and top are flat and of large areas for close fitting engagement with large areas of their respective plates, so that the flask will be eiectively heated by conduction. The two heating elements are wired to a thermostat and a time controlled switch so that the temperature of the plates may be accurately controlled, with the time controlled switch acting to eliminate the necessity of personal attention. The metal plates are heated by radiation and are interposed between the flask and the two heating elements. I have found that such a plate system operates to heat the ilask elciently and maintain a uniform temperature condition, with the dry heat system resulting in perfect dentures without the aid of tin foiling.

In practice, the denture cast or mold is positioned in the bottom section of the ilask, with the section previously provided with the usual plaster of Paris or other material common in the rt. The plaster is permitted to set and is treated with a separating fluid in the usual manner.. The upper section is then placed in position on the lower section vand a creamy mixture of plaster of Paris is poured into the upper ilask section, after which the cover is placed on the upper section. The flask is then set aside to permit the plaster of Paris to harden.

After the plaster of Paris has set, the flask is placed in the oven and heated until the wax in which the teeth are set is soft and can be removed from the mold. At this time all the teeth are removed from the mold and kept in their proper arrangement, and any remaining wax in the mold is removed. The ilask sections are placed in an oven for dehydration purposes. I have found that subjecting the ilask sections to a temperature of 300 F. for a period of approximately two hours is suilicient for proper dehydration thereof.' However, the ilask sections are separated for dehydration purposes, and proper dehydration does not depend upon the two-plate feature employed in the dry heat curing stage.

After dehydration, the ilask sections are permitted to cool for a few minutes and the plaster, with the exception of the areas occupied by the teeth, is painted with a coating of suitable varnish in the usual manner. The teeth are then placed in position and the flask sections again placed in the oven Tor approximately ten minutes at a temperature of about 215 F. The sections are separated in the oven and when removed, the section of the ask containing the teeth is provided with the required amount of denture material around the teeth and completely filling the mold. As the denture material assumes a semi-liquid condition, the other section of the flask is removed from the oven and placed in position on a companion flask section. The sections are then pressed together' and latched, after which the latched flask is placed in the oven for curing purposes. During the heat curing, the two metal plates are einployed, as previously mentioned, and the thermostat is set for the temperature required for the particular type of denture material being used. Such temperatures vary with respect to different materials and are designated by the manufacturers of the respective materials. After thel curing stage, the ask is. permitted to cool and the trimming, filing and polishing of. the dent-ure are. done in the customary manner.

In Lthe accompanying drawings:

Figure 1- is a, sectional view of an oven` in accordance with my invention;

Figure 2- is a sectional view taken substantially along the line 2-2 of Figure l, with the ask illustrated in elevation;

Figure- 3 is a detail View of the thermostat control; Y Y

Figure4is a sectional view taken substantially along the line 4--4 of Figure l; and

Figure 5 is a diagrammaticviewof the electric circuit.

In the embodiment selected to illustrate my invention, the.l oven.` I0.l comprisesl a bottom. wall.

|.;2,1 a. topi wally I4, arear. wall |61 and. sidewalls.

|8;. The fronixcf the oven isfopen and. isl nor mallyfclosedbya doorV 20, hingedly connected. at

2,2 vwiththe bottom wall I2.

All the walls and the door are identicalr in construction and each comprises an inner metallic plate 24 spaced from an outer: metallic plate 26, with the space between the plates lled with insulating'material28; Rear wall I6*A is slightly thicker than the other wallsofthe oven to provide accommodationfor the wiring of the heating-elements.

' To one ofthe inner'plates` 24 I fixedly securea relatively thick metal plate 3|)V through the medium 'of' screws 32, which plate serves as aA Plate BIleXtends'V the full width ofthei oven chamber 3|/butr ter-' shelf for the dental ask 34.

minates slightly` shortA of the door 28, see Figs; 2 and'rl; Upon the ask 34 I position a relatively heavy; metallic plate 38, which plate is of' the.-

same.` size and conguration asv the plateV 38, the

onlydiference being that plate BU'ispermanently secured ina xedposition whilethe platev 38 is. free.: and maybe removed from-the chamber. 36 to facilitate` placement? andriremovalof thel flaskv 34; The -iiaskhas i, a nat bottom 48 resting; onY the plate. Iffandgav flattop: 42 .fon;whichvthez.plate 38' rests;

Beneath the platef. 3|)A I mount two heating units ofthebottom wall |2through themedium: ofi spacing sleeves 52, and bolts-54 extend through" thegsl'eeves 52, the plate 24? and ther metallic sheaths'rof' their respective heatingunits 44? and-46 for xedlysecuringy the latterin'spaced relation with the plate 24. Similarly, the heating units 48 and 56 are Xedly secured to the plate 24 of the top wall I4 through the medium of sleeves 58 and bolts BIJ. Heating units 48 and 50 also include metallic sheaths 56.

Referring to Fig. 4, the heating unit 5|] is illustrated partly in section and includes insulator bodies 62 and 64 which support a resistance conductor 66 runningY back and forth between the bodies. The bodies are grooved at 68 for housing the ends of the different lengths of the resistance, and the body 62 has a lug 16 and the body 64 has two such lugs 12 about which the resistance is looped. Sheath 56 is filled with suitable heat refractory insulating material 14. The ends of the resistance 66 are connected with terminals 16 provided with terminal screws 18 to respectively connect the terminals with wires 80 and 82. All the heating units 44 to 56 are identical inconstruction.

Wire 88 is connected with a bimetallic strap 84 of a thermostat 86 and isr secured between insulating blocks 88, see Fig. 2. The thermostat includes a second metallic strap 90 secured between one of the insulating blocks 88 and an insulating block 92, with the blocks 88 and 92 and the two straps 84 and 98 clamped into a unitary structure by Vbolts 94 anchored to a bracket 96 which is welded to the plate24 of the top wall. |4. Bolts 94 clamp an arm 98 against the blocksV 92, and an adjusting screw |80 is threaded into the arm 98 and engages an insulating pad |92 mounted on the strap 96. Straps 84` and 98 areV respectively provided with contact points |84. Strap 90 may be adjusted relatively to the strap 84 through adjustment of the screw H10' Wire` 82 is.` connected with lone terminal-screw 18. of the resistance 66 in `the-heating unit 48, best illustrated in Fig. 5. The other terminal. screw 18 of the -heating unit 48 is-connectedwith the strap 84 through the mediumof a wire |06 The terminal screw 18 connected with the wire ICIS-isl connected with a wire |08 connected with a w-irefI I0 leading to a'pilot lamp I |24. Lamp |I2 is connected with awire ||41connected with a wire I I6, which wire is connected'with a-wire I |8 connected with the terminal 18 of the heating unit 48' connected with the wire 82e. A wire |29 is connected with the wires |09 and I I0 and withl one of the terminals 18 of" the resistance 66 in the heating unit 44, and this terminal is connected with a wire |22 connected with the terminal 18 of the resistanceA 66 in the heatingunit 46; The second terminal 18" of the heating unit' 44 is connected with a wire |24 connected with'- the second terminal 18" of the heating unit 46. The'terminal 18l of the heating unit'44fconnected with the wire |24 ist connected with a wire |26- whichis also connected with the' wires I I4, IIB and"||8.

Aline wire |28' is" connected with the'wi're; I I6 aswell as' a wire |36v connected-with a' terminal |32' of a three-terminal receptacle`V |34v secured Ato the plate 26 of the rear wall I6. A wire |36' elec'- tricallyconnects the strap' 98 with the second terminal |38 of the receptacle |34', andthethirdf terminal |40 of the receptacle is electrically connected with the second linev wire' |42. Three wires |44, |46 and |48 are respectively provided with prongs |58, |52 and |54 for engagement with the terminals |32, I381and |46, respectively. The three wires |44, |46Va-nd |49-may`be-incorporated in a single cord for connection with anelectric clock or timing device '|581 Such clocks are old and well known in the art and need not be described in detail. Sulce it to say that the clock includes a motor |58 electrically connected with the wires |46 and |48, with the latter wire connected with a terminal |60 of the clock actuated switch |62. The wire |44 is connected with the second terminal |64 of the switch |62.

Wire |36 connected with the strap 90 is electrically connected with the line wire |42 through the medium of the terminal |38, prong |52, Wire |46, motor |58, wire |48, prong |54 and terminal |40. Fig. illustrates one terminal 18 in each of the heating units 44 to 50 as being electrically connected with the bimetallic strap 84. The second terminals of all the heating units are connected with the wire ||6 which is connected with the line wire |28. Thus, when the prongs |50, |52 and |54 are pressed into the socket |34, and the switch |62 is closed. the clock may be set to maintain the switch |62 closed for a predetermined length of time and the pilot lamp 2 indicates a closed circuit through the resistances 66. During operation, the temperature of the heating units 44 to 50 is controlled through the medium of the thermostat 86. Strap 80 may be adjusted to cause separation of the contacts |04 upon predetermined bending of the strap 84.

A knob |66 is secured to the screw |80, and the screw is rotatably mounted in a sleeve |68 in the top wall |4. Fig. 3 illustrates the knob |66 as being provided with graduations |10 for indicating different temperature positions of the knob when rotated about the axis of the shaft |08. The plate 26 of the top wall |4 is provided with a pointer |12 to which the different graduations may be adjusted.

Wall |6 is provided with a tube |14 which places the chamber 36 in communication with the atmosphere. Tube |14 may be closed by inserting a plug therein during the heat curing stage. However, in cases Where the flask sections are being dehydrated, the plug is removed to vent the moisture to the atmosphere.

Flask 34 is illustrated as comprising sections |16 and |18, with a cover |80 fitting on the section |18. Sections |16 and |18 are provided with bores |82 Within which pins |84 flxedly connected with the cover |80 are slidably receivable. Flask section |16 and the pins |84 are provided with transverse openings |86 for the reception of pins |88 which secure the pins |64 against retraction so that the flask sections and the cover are effectively connected into a unitary structure for heat treating purposes. The manner in which the flask sections and the cover are latched eliminates the necessity of a press inside the oven, and the plate 38 may be laid on the flask so that the latter constitutes a support for the plate. Accordingly, I eliminate the necessity of special mountings for the plate 38 and the weight of the plate is utilized for bringing the plate into effective pressure relation with the flat face 42.

Having thus described certain embodiments of my invention in detail, it is, of course, understood that I do not desire to limit the scope thereof to the exact details set forth except insofar as those details may be defined in the appended claims.

I claim:

1. In combination with a dental flask, a heating chamber for containing the dental flask, a heat conduction shelf inside the chamber for supporting the dental flask, a free heat conduction plate adapted to lie at rest on the dental flask, and heat radiating means for said shelf and plate.

2. In combination with a dental flask, a heating chamber for containing the dental flask, a heat conduction shelf inside the chamber for supporting the dental flask, a free heat conduction plate adapted to lie at rest on the dental flask, and a plurality of heat radiating means for said shelf and said plate.

3. In combination with a dental flask, a heating chamber for containing the dental flask, a heat conduction shelf inside the chamber for supporting the dental flask, a heat conduction means adapted to lie at rest on the dental flask, and heat radiating means for said shelf and means.

4. In combination with a dental flask, a heating chamber for containing the dental flask, a heat conduction shelf inside the chamber for supporting the dental flask, a heat conduction means adapted to lie at rest on the dental flask, and means for heating said shelf and means.

5. In combination with a dental flask, a heating chamber `for containing the dental flask, a heat conduction shelf inside the chamber for supporting the dental flask, a heat conduction plate engaging the top of the dental flask, and means for heating said shelf and plate.

6. In combination with a dental flask, an oven for containing the dental flask, a heat conduction shelf inside the oven for supporting the dental flask, a heat conduction plate engaging the top of the flask, and heat radiating means for said shelf and said plate, said heat radiating means lying beneath said shelf and above said plate,

7. In combination with a dental flask, an oven for containing the dental flask, a heat conduction shelf inside the oven for supporting the dental flask, a heat conduction plate engaging the top of the flask, heat radiating means for said shelf and said plate, said heat radiating means lying beneath said shelf and above said plate, said heat radiating means comprising electrical resistances, an electric circuit for supplying current to said resistances, and a thermostat interposed in said electric circuit.

8. In combination with a dental flask, an oven for containing the dental flask, a heat conduction shelf inside the oven for supporting the dental flask, a heat conduction plate engaging the top of the flask, heat radiating means for said shelf and said plate, said heat radiating means lying beneath said shelf and above said plate, said heat radiating means comprising electrical resistances, an electric circuit for supplying current to said resistances, a thermostat interposed in said electric circuit, and a time controlled switch interposed in said electric circuit.

9. In combination with a dental flask, an oven for containing the dental flask, a heat conduction shelf inside the oven for supporting the dental flask, a heat conduction plate engaging the top of the flask, heat radiating means for said shelf and said plate, said heat radiating means lying beneath said shelf and above said plate, said heat radiating means comprising electrical resistances, an electric circuit for supplying current to said resistances, a thermostat interposed in said electric circuit, a time controlled switch interposed in said electric circuit, and a pilot lamp interposed in said electric circuit.

l0. In combination with a dental flask, an oven for containing the dental flask, a heat conduction shelf inside the oven for supporting the dental flask, a heat conduction plate engaging the top of the flask, heat radiating means for said shelf and said plate, said heat radiating means lying beneath said shelf and above said plate, said heat radiating means .Comprising-electrical resstana an electric circuit-for supplying current v.tosaid re.-

sistances, a thermostat interposed in `said electric relation, a heatingoven for-containing the dental.

flask, a heatconduction shelf insidevtherchamber for supporting the dentalflask, a free heat conduction-plate Aadapted to-lieatreston the dental flask, and'means for heating said shelf and plate.

.-12.2 An oven for-,the dry heat curngof articial dentures comprising a relatively .thick first plate Xedly-secured inside the oven for supporting a dental flask, afsecond relatively-thick `plate adaptedvtovengage the top of the flask, said' first and second plates beingrespectively spaced from the bottomand top of the1oven, an electrical heatingunit located underneath said first plate, an electrical heating unit located above said. second plate, said rst'and secondplates being ar.- rangedinheat conducting engagement With the flask, saidheating units being arranged in heat radiating relation with their respectivefirst and second platesandan electric circuit operatively` connectedvvith said heating units.

* 13. An .oven for the. dryheatcuring of artificial dentures comprising a relatively thick first I platefixedlysecuredinsidethe oven forfsupport-` ingA adental iiask,.a second relatively .thick plate adaptedto engage the top of the flask,said first and second plates being respectively spaced from the bottom and top of the oven,e1ectrical heating units located underneath said first plate, electrical heating units located above said second plates, saidV first and second plates beingv arranged in heat conducting engagementwith the ask',said heating. units being arranged inA heatrradiating relation with theiry respective rst and second plates, and an electric. circuit operatively connectedwith saidheating-units.A

, 14` An oven for the dry heat curing of .arti-V ficial dentures comprising a relatively-thick first plate xedly secured inside thel oven for-supporting a dental flask, a second relatively thick plate adapted to engage the top of the-flask, said first and second plates being respectively spaced. from the bottom and top of the oven, electrical heating units located-underneath said first plate, electrical heatingunits. located above said second plates, said first and secondrplates being arranged inheat conductingengagement With theyflask, saidl heatingfunits. being arranged in heat radiating relation with their respective.. first and second plates, an electric circuitoperatively connected with said heating units, said oven having a. door providing a Wall'for the oven, and said plates beingv spaced from` the door.

AVERY H. CHENOWETH. 

